1. Field of the Invention
The invention relates to stepping actuators and to methods for the formation of such stepping actuators. The stepping actuators according to certain embodiments of the present invention may be operated at voltages of 15V or lower.
2. Technical Background
Actuators are mechanical devices for moving or controlling a mechanism or system. They are devices which transform an input signal (mainly an electrical input signal) into motion. Specific examples are electrical motors, pneumatic actuators, hydraulic pistons, relays, piezoelectric actuators, digital micromirror devices (DMD) and electroactive polymers.
Linear actuators are devices used to generate controlled physical linear displacement. Linear stepping actuators can provide long-range motion with relatively high force. Movements or displacements can be obtained using a variety of mechanisms such as electrostatic force, piezoelectric deformation and elastic deformation.
Transforming an out-of-plane movement to an in-plane movement was reported by E. Sarajlic et al. (IEEE 13th Intl. Conf. on Solid-State Sensors, Actuators and Microsystems, Korea Jun. 5-9, 2005, p 53-56), M. P. de Boer et al. (J. of Micromech. Syst. 13, 63-74, 2004), and N. Tas et al. (IEEE Intl. Conf. on Solid-State Sensors and Actuators, Chicago Jun. 16-19, 1997, p 777-780).
One type of linear actuator is a MEMS actuator, which are popular in micro-positioning applications for their long ranges. MEMS actuators are especially useful in several large range micro-positioning applications such as data storage, micro-robots, microsurgery and micro-needle position. Stepping actuators are good candidates for these applications because they can provide very large ranges with their latch-drive topology, e.g. more than 20 μm, for example up to 35 μm, or even up to 1 mm.
However, until now such stepping actuators could not be considered for in vivo biomedical applications because of their required high input voltages.
Shuffle motors are also promising for their ability to achieve large positioning ranges. This is realized by the pull-in based operation and toothless latching. However, currently available shuffle motors still use relatively high operating voltages (40 V or more). This may be caused by the out-of-plane behavior of these motors: out-of-plane deflection is converted to in-plane deflection and this step deflection is maintained with friction forces. These high voltages still make them unsuitable for being used for in vivo applications.
To achieve low voltage operation, the shuffle motor can be built with a thin (thickness lower than 3 μm) out-of-plane deflecting plate and/or a large capacitance electrode. However, both solutions will cause problems such as, for example, buckling of the actuator.